Preheat oven to 350 degrees F (175 degrees C). Lightly grease a medium casserole dish.
Heat the oil in a skillet over medium heat. Place chicken in skillet, and cook 10 minutes, or until juices run clear. Drain, and transfer to the prepared casserole dish. Mix with mayonnaise, water chestnuts, pimentos, almonds, celery seed, and lemon juice. Season with garlic salt to taste. Layer with cheese, and top with French-fried onion rings.
Bake 30 minutes in the preheated oven, until cheese is melted and onion rings are lightly browned. If rings start to get too brown, put foil on casserole or lower oven rack. Watch carefully, or onion rings will burn.
